A fixing

ABSTRACT

A ratchet fixing 5 for connecting an insulation layer 4 to a precast concrete panel 2, a precast concrete panel system 1 comprising the fixing 5 and a method for forming an insulated precast concrete panel system 1 comprising fixing an insulation layer 4 to a concrete panel 2 with fixings 5 in which the fixing 5 is made up of an insulation layer penetrating portion 18 and a concrete penetrating portion 19 contiguous with the insulating layer penetrating portion 18, the insulation layer penetrating portion 18 having a disc-like tension head 20 for abutting against the outer surface of the insulation layer 4 and a pawl 22 and ratchet 25 for securing the tension head 20 to the insulation layer penetrating portion 18.

INTRODUCTION

This invention relates to a fixing for connecting an insulation layer toa precast concrete panel and to a precast concrete panel system made upof the concrete panel and the fixing. The invention also relates to amethod for forming an insulated precast concrete panel.

BACKGROUND

Precast concrete panels for walls, floors, ceilings and the like areincreasingly used in the construction of industrial, commercial andresidential buildings. Most commonly, the precast concrete panel isformed off-site and then delivered to a construction site for assembly.

Precast concrete wall panels are generally manufactured on the flat inwooden concrete decks or forms sized to define the perimeter of theconcrete panel.

A grid of steel rebar can be constructed and tied in-place within theform to reinforce the panel. Embeds for attaching the structural panelto footings, other panels, columns, slabs, roof systems, or forreceiving building accessories and inserts which serve as attachmentpoints for lifting hardware and temporary braces can also be provided inthe form. Anchor-like fixings can also be employed to secure insulationto the concrete.

Concrete is then poured into the form in the same manner as floor slabsand is then finished as required e.g. a trowel finish or other types ofarchitectural finishes and patterns.

Precast concrete panels offer a number benefits for construction. Whilstenjoying the benefits of being formed from concrete, the panels can bemanufactured consistently and reproducibly with the high degree ofaccuracy required in modern construction. The pre-cast panels can thenbe rapidly assembled at building sites facilitating rapid builds.

Generally, precast concrete wall panels fall into three basiccategories: sandwich, thin-shell and solid while the wall panels can bedesigned as non- loadbearing or loadbearing, carrying floor and roofloads, as well as lateral loads.

As indicated above, precast concrete panels are typically manufacturedoff-site, although the panels can be manufactured on-site, and thenecessary external finishes, such as plaster boarding and plastering,and services, such as electrics and plumbing, fitted followinginstallation of the panels on-site.

The precast panels must also be insulated when used for domestic,institutional and commercial buildings. In sandwich panels, rigidinsulation is sandwiched between two layers of concrete. The insulationthickness can vary to create the desired thermal insulating property(“U” value, or known as ‘IR’ value in the United States) for the wall.However, sandwich panels are relatively expensive and more timeconsuming to manufacture due to the multiple layers of concreterequired. Moreover, as the insulation is placed between two layers ofconcrete, a significant risk exists that undesirable levels of thermalbridging can occur across the pre-cast panel.

Thin-shell wall panels consist of a thin outer-layer of concreteconnected to a back-up system typically constructed of steel framing orconcrete which connects the wall panel to the building structure. Alayer of rigid insulation is generally placed between the exterior layerof concrete and the back-up system. However, thin-shell wall panels canalso be expensive and slow to produce due to the relatively complexnature of the required back-up system and multiple layers required.

Solid precast concrete wall panels are typically formed from a singlesolid concrete layer and as such are quicker and less expensive toproduce than sandwich or thin shell precast panels. Insulation can befixed to the pre-cast panel wall insulation anchors following removal ofthe precast panel from its form. However, the manual fixing ofinsulation to the precast panel following removal from the formintroduces another step to the manufacturing process can slow downmanufacture and increase the risk of thermal bridging. Alternatively, asdescribed in Specification U.S. Pat. No. 8,555,584, an insulation layerprovided with rigid anchors which also serve to support the steel rebarcan be included in the form during casting of the panel. However, due tothe rigid nature of the anchor, the anchor can fail duringexpansion/contraction of the concrete during curing while contact of theanchor with the steel rebar can result in thermal bridging across thepanel. European Patent Specification No. 3,106,579, German PatentSpecification No. 101 18 678, Specification U.S. Pat. No. 5,660,015 andPCT Patent Specification No. WO 2017/116237 all describe similar fixingmethods in which fixings can be retrofitted to existing concretesubstrates in a manner requiring the use of labour-intensivepre-drilling steps, nail guns, fastening guns and the like.

In short, conventional block on flat construction methods are slow whileknown precast panels suffer from a number of disadvantages—e.g.structural insulated panels (SIP's) require a cavity and outer layer ofblockwork and insulated structural panels (ISP's) require an inner layerof concrete coupled with an outer layer of concrete and insulated core.Moreover, all of the above construction methods are labour intensive andrequire skilled on-site construction while all suffer from excessivethermal bridging.

SUMMARY

According to the invention there is provided a fixing, as set out in theappended claims, for connecting an insulation layer to a precastconcrete panel comprising:

-   -   an insulation layer penetrating portion and    -   a concrete penetrating portion contiguous with the insulation        layer penetrating portion wherein the insulation layer        penetrating portion comprises a flexible tie.

Suitably, the insulation layer penetrating portion further comprises atension head attachable to the flexible tie. The tension head can haveone or two pawls depending on pull off requirements and wind loads onlarger residential buildings.

Preferably, the flexible tie comprises a ratchet attachable to thetension head at a pawl. Advantageously, the ratchet comprises throughholes in the tie.

Preferably, the pawl comprises a slot in the tension head. Suitably, thetension head comprises a collar surrounding the slot.

Preferably, the tension head comprises indents to define finger grips inthe tension head.

Suitably, the concrete penetrating portion comprises a wall plug.

Preferably, the wall plug comprises a substantially cylindrical head.More preferably, the substantially cylindrical head comprises at leastone laterally extending fin for maximizing grip of the wall plug onconcrete. Advantageously, the substantially cylindrical head comprisesat least one notch for maximizing grip of the wall plug on concrete.Alternatively, the wall plug comprises a substantially T-shaped head.

Preferably, the concrete penetrating portion comprises a flange forstabilising the fixing in position during concrete pouring. Morepreferably, the flange extends laterally outwards from the concretepenetrating portion.

In one embodiment, the fixing comprises at least one rib forstrengthening the fixing. Preferably, the at least one rib is providedon the insulation layer penetrating portion. Alternatively or inaddition, the at least one rib is provided on the concrete penetratingportion.

The invention also extends to a precast concrete panel system comprisinga fixing as hereinbefore defined.

Preferably, the precast concrete panel system comprises a precastconcrete panel reinforced with rebar and insulation fixed to the precastconcrete panel by the fixing wherein the rebar and the fixing arespatially separate within the system.

More preferably, the insulation layer comprises insulation board. Mostpreferably, the insulation board comprises expanded polystyrene.

In a further embodiment, the invention also extends to a method forforming an insulated precast concrete panel system comprising fixing aninsulation layer to a concrete panel with fixings as hereinbeforedefined.

Preferably, the method comprises fitting the fixings to the insulationlayer via the insulation layer penetrating portion, laying theinsulation layer in a deck and pouring concrete into the deck toencapsulate the concrete penetrating portion of the fixings.

Suitably, the method further comprises the step of constructing a rebarin the deck before pouring the concrete.

Preferably, the rebar is spatially separated from the fixings to preventthermal bridging.

The invention meets and exceeds modern building regulation requirementsfor both domestic and commercial projects by enabling a fast, energyefficient/thermal bridge free construction. The fixing and associatedprecast panel system of the invention eliminate the need for themajority of skilled on- site labour thus providing a faster constructionmethod.

The fixing and precast concrete panel system of the invention formedwith the fixing exhibit minimal thermal bridging as compared with thefixings and insulated precast concrete panels of the prior art. Inparticular, the flexibility of the tie of the insulation penetratingportion of the ratchet fixing of the invention offers room for expansionand contraction during concrete curing thereby preserving the structuralintegrity of the system and eliminating the risk of thermal bridgingcaused by damage to ties and/or insulation during curing. Moreover, asthe ratchet tie is structurally and spatially separated from andindependent of any steel rebar employed in the precast concrete panel,the method for forming a precast concrete panel system eliminates thelikelihood of thermal bridging through fixings and rebars. Theratcheting action of the ratchet tie also allows the tie to adapt toinsulation of varying thicknesses whilst also enabling secure attachmentof the insulation to the solid concrete panel.

Moreover, the solid precast concrete panel system and associated methodfor forming the system of the invention do not require the use ofsandwiched layers of insulation resulting in an insulated concrete panelthat is easier to form and manufacture to a high degree of accuracy withoptimal thermal characteristics. The solid precast concrete panel of theinvention is also relatively inexpensive to manufacture compared withsandwich and thin shell concrete panels.

The insulated precast panel systems of the invention can be formedoff-site regardless of weather conditions and can then be rapidlyassembled on site with significantly reduced skilled labourrequirements. Accordingly, construction projects can be completed soonerand faster than with conventional construction methods.

In summary, the fixing of the invention can be installed, pre-pouring ofconcrete with minimal effort. Moreover, as insulation can be providedwith suitable perforations to receive the fixings, no drilling or steelnail fastening is required when employing the fixing. Accordingly, thefixing of the invention dramatically reduces the need for onsite labourand allows for the delivery of a factory made fully structural insulatedconcrete panel that is of monolithic construction. The flexible plasticsfixings of the invention, being separate from the structural steel andthe like, minimise the risk of thermal bridging compared with thefixings and methods of the prior art. The fixing of the invention isalso suitable for use with all concrete types.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood from the followingdescription of an embodiment thereof, given by way of example only, withreference to the accompanying drawings, in which:-

FIG. 1 is a cross-sectional view through a precast concrete panel systemof the invention made up of a precast panel adapted to define a windowopening for receiving a window in which the precast panel is laid on theflat and has an upper concrete layer over a lower insulation layer andthe insulation layer is anchored to the concrete panel by a two-partratchet fixing/anchor extending between the insulation layer and theconcrete panel;

FIG. 2 is an external plan view of the precast panel system of FIG. 1from the insulation layer side of the precast concrete panel with therender finish omitted to reveal the tension heads of the multipleratchet fixings visible on the insulation layer;

FIG. 3 is a partially cutaway view of the precast concrete panel of FIG.2 showing the wall plug of the ratchet fixings embedded in the concretelayer;

FIG. 4 is an enlarged perspective view from above and one side and fromthe concrete penetrating portion of the ratchet fixing;

FIG. 5 is a perspective view from above and one side of the two-partratchet fixing of FIG. 4 with the tension head of the ratchet fixingremoved i.e. before use of the ratchet fixing;

FIG. 6 is a perspective view from above and one side and from theinsulating penetrating portion of the ratchet fixing;

FIG. 7 is a perspective view from above and one side and from theinsulating penetrating portion of the two-part ratchet fixing with thetension head removed i.e. before use of the ratchet fixing;

FIG. 8 is a plan view of the ratchet fixing;

FIG. 9 is a perspective view from above and one side of a secondembodiment of a fixing of the invention, with the tension head omitted,in which the wall plug of the concrete penetrating portion issubstantially T-shaped and the fixing is provided with stabilising andstrengthening ribs to reinforce the fixing;

FIG. 10 is an enlarged perspective view from above and one side of thetension head of the fixing of FIG. 9;

FIG. 11 is a side elevation of the tension head of FIG. 10;

FIG. 12 is a cross-sectional view through the tension head of FIG. 11,and

FIG. 13 is an enlarged side elevation of the T-shaped wall plug of theconcrete penetrating portion of the fixing of FIG. 9 with strengtheningribs provided adjacent the stabilising flange of the wall plug on theinsulation penetrating portion.

DETAILED DESCRIPTION OF THE INVENTION

As shown in the drawings, a precast concrete panel system of theinvention is generally indicated by the reference numeral 1 and (whenviewed on the flat as shown in FIG. 1) is made up of a precast panel 2having an upper concrete layer 3 and a lower insulation layer 4typically of expanded polystyrene or similar secured to the concretelayer 3 by a first embodiment of a two-part ratchet anchor or fixing 5of the invention. The concrete layer 3 is also provided with a grid ofsteel rebar (not shown) to reinforce the precast panel 2 while anexternal render finish 6 is provided on the outer surface of theinsulation layer 4 and plasterboard 7 is mounted over a cavity 8 definedby timber stud 9 at the outer face of the concrete layer 3. The cavity 8contains internal insulation material 10.

As shall be explained more fully below, the ratchet fixing 5 securelyattaches the insulation layer 4 to the concrete layer 3 and isindependent of the grid of steel rebar i.e. does not contact the grid ofsteel rebar thereby minimising thermal bridging across the panel systemof the invention whilst, being flexible, the ratchet fixing 5 offersroom for expansion and contraction of concrete during curing.

The precast panel 2 is shaped to define scarf joints 11 forinterconnecting individual precast panels 2 during the construction of abuilding.

As shown particularly in FIG. 2, the precast panel 2 is substantiallyrectangular in shape and has a bottom edge 12, a top edge 13 and firstand second side edges 14,15 connecting the bottom and top edges 12,13. Awindow opening 16 is defined in the precast panel 2 for receiving awindow 17.

FIGS. 4 to 8 show enlarged views of the first embodiment of the ratchetfixing 5. As shown in the drawings, the ratchet fixing 5 is made up ofan insulation layer penetrating portion 18 and a concrete penetratingportion 19 contiguous with the insulation layer penetrating portion 18.The insulation layer penetrating portion 18 has a disc-like tension head20 for abutting against the outer surface of the insulation layer 4 asshown in FIGS. 2 and 3 and for urging the insulation layer 4 against theconcrete layer 3 in use. The tension head 20 has a rectangular centralslot 21 which defines a pawl 22 while a series of circular openings 23are arranged circumferentially around the central slot 21.

The insulation layer penetrating portion 18 is also made up of asubstantially rectangular elongate flexible tie 24 which extends betweenthe tension head 20 and the concrete penetrating portion 19. Moreparticularly, the flexible tie 24 is insertable in the central slot 21of the tension head 20 and is securely attachable to the pawl 22 in thecentral slot 21 via a ratchet 25 formed in the flexible tie 24. In thepresent embodiment, the ratchet 25 is defined by through holes ornotches 26 in the flexible tie 24. However, as will be appreciated bythose skilled in the art, the ratchet 25 can be defined by teeth orsimilar structures on the tie 24 if desired.

The concrete penetrating portion 19 is made up of a circular stabilisingflange 27 extending laterally outwards from the concrete penetratingportion 19 for stabilising the ratchet fixing 5 in position duringconcrete pouring. The circular stabilising flange 27 has a diametersmaller than that of the tension head 20. A wall plug 28 is mounted onthe stabilising flange 27 for anchoring and embedding the concretepenetrating portion 19 in the concrete layer 3 of the precast panel 2.As shall be explained more fully below, the concrete penetrating portion19, and in particular the wall plug 28, is encapsulated in the concretelayer 3 during manufacture of the precast panel system 1 of theinvention.

In order to provide a highly effective anchor in the concrete layer 3,the wall plug 28 is made up of a substantially cylindrical head 29having a pointed tip 30 and first and second pairs of laterallyextending fins 31, 32 respectively for maximising grip in the concretelayer 3. The cylindrical head 29 is also provided with a first andsecond pair of notches 33, 34 respectively between the fins 31, 32 tofurther enhance the grip of the wall plug 24 in the concrete layer 3.

FIGS. 9 to 13 show a second embodiment of a ratchet fixing 5 of theinvention similar to the ratchet fixing of FIGS. 1 to 8 and likenumerals indicate like parts. However, in the present embodiment, thewall plug 28 of the concrete penetrating portion 19 is substantiallyT-shaped and the ratchet fixing 5 is provided with stabilising andstrengthening ribs 36 to reinforce the ratchet fixing 5. As shown in thedrawings, in the present embodiment, three strengthening ribs 36 areprovided on the insulation penetrating portion 18, and more particularlythe elongate tie 24, adjacent the stabilising flange 27. Thestrengthening ribs 36 extend laterally outwards from the longitudinalaxis defined by the elongate tie 24 to strengthen engagement between theratchet fixing 5 and insulation layers 4 in use i.e. the laterallyextending ribs 36 increase surface contact between the ratchet fixing 5and the insulation layer 4 to assist in stabilising the ratchet fixing 5in the insulation layer 4 whilst still allowing the elongate tie 24 toflex in the insulating layer 4.

If desired, additional or alternatively positioned strengthening ribs 36can be provided on the insulation penetrating portion 18.

In the present embodiment, the circular tension head 20 of the ratchetfixing 5 is provided with peripheral indents 37 to define finger grips38 for gripping and positioning the tension head 20 in use. The tensionhead 20 is also provided with a central collar 39 surrounding thecentral slot 21. The central collar 39 serves to assist in supportingthe elongate tie 24 in the toothed pawl 22 of the rectangular centralslot 21 in use.

As shown particularly in FIG. 13, the wall plug 28 is formed as asubstantially T-shaped head 40 to assist in anchoring the concretepenetrating portion 19 in concrete. The T-shaped head 40 has an uprightportion 41 and an arcuate “cross” or transverse portion 42. The arcuatetransverse portion 42 is curved towards the upright portion 41 and theflange 27 to assist in strengthening the anchoring relationship betweenthe ratchet fixing 5 and the concrete layer 3 in use. The uprightportion 41 and the arcuate transverse portion 42 of the T-shaped head 40are further provided with head ribs 43 to further enhance surfacecontact with the concrete layer 3 and acts to maintain rigidity of thefixing 5.

The ratchet fixing 5 of the present embodiment can be easily and simplymanufactured using injection moulding techniques.

The precast concrete panel system 1 of the invention can be manufacturedby first constructing a form or deck on the flat in accordance with theshape and size of precast panel 2 required. The deck is made up ofsupporting sides having a depth greater than the final depth required inthe precast concrete panel 2. By way of example for a precast panelsystem 1 as shown in FIG. 2 having a height of 2400 mm, a width of 2200mm and a thickness of 150 mm. The total thickness can be 370 mm,comprising 4 mm Hard wall Internal Finish, 12.5 mm Plaster boarding, 44mm Timber Battens, 150 mm Reinforced Concrete, 150 mm EPS Insulation, 9mm External Rendering with Reinforced Fiberglass Mesh cloth and Finishedusing a Silicone Topcoat. An insulation layer 4 in the form ofpre-formed perforated insulation boards 4 (e.g. expanded polystyrene),suitable for use with the ratchet fixing 5 are then fitted with thedesired number and layout of ratchet fixings 5.

In particular, elongate ties 24 of the ratchet fixing 5 with the tensionhead 20 removed as shown in FIGS. 5 and 7 are inserted through theinsulation boards 4 so that the free end 35 of each elongate tie 24 isat the outer surface of the insulation layer 4 as shown in the drawingsand the stabilising flange 27 of each concrete penetrating portion 19abuts the opposite internal face of the insulation layer 4. The tensionheads 20 are then engaged with the free end 35 of each elongate tie 24by inserting the free ends 35 of the elongate ties 24 in the centralslots 21 of the tension heads 20 so that the pawls 22 in the centralslots 21 irreversibly engage the ratchets 25 on the elongate ties 24.The engagement of each pawl 22 and ratchet 25 can be tightened as neededto increase grip or tension across the insulation layer 4 as required.

The insulation boards 4 are then laid face down in the deck i.e. withthe tension heads 20 disposed downwards and the wall plugs 28 disposedupwards in the deck. Upon completion of the above steps, concrete isthen poured into the deck to encapsulate the wall plugs 28 of theratchet fixings 5 and the steel rebar structural support. The resultantprecast concrete panel system 1 is a structurally sound, highlyinsulated structure which exhibits minimal thermal bridgingcharacteristics of about 0.002 W/m²K or greater and which is suitablefor delivery to a construction site for building construction.

If desired, a rebar can be constructed in the deck before pouringconcrete e.g. in the present example a grid of steel rebar made up 50×6mm iron ribs placed around the edges of the deck and at centres that donot interfere with the ratchet fixings 5 during manufacturing can beincorporated into the deck.

The ratchet fixing 5 can be formed from any suitable material such asplastics, nylon and the like and can be sized as required. For example,for the precast concrete panel system described above in FIGS. 1 to 8, aratchet fixing 5 having an overall length of about 203 mm is suitablewith the tension head having a thickness of about 3 mm, the elongate tie24 having a length of about 150 mm, the stabilising flange 27 having athickness of about 5 mm and the concrete penetrating portion 19 and inparticular the wall-plug 28 having a length of about 50 mm for embeddingin the concrete layer 3 and a maximum width of about 30 mm. Such aratchet fixing 5 exhibits thermal bridging of less than half that ofknown fixings which, at best, exhibit thermal bridging of about 0.02W/m²k. It is envisaged various lengths ranging from 250 mm up to 400 mmcan be embodied depending on U-value requirements and insulationoptions. For example, the ratchet fixing of FIGS. 9 to 13 can have aninsulation layer penetrating portion 3 length of about 310 mm, a wallplug length of about 30 mm, a T-shaped head 39 width of about 35 mm andthickness of about 13 mm, a flange 27 diameter of about 28 mm, a tensionhead 20 diameter of about 60 mm and thickness of about 11 mm.

In an embodiment there is provided a conical flange positioned near theinside of the tension head, whose function is to hold a second or astronger pawl depending on kN/mm required.

In the specification the terms “comprise, comprises, comprised andcomprising” or any variation thereof and the terms include, includes,included and including” or any variation thereof are considered to betotally interchangeable and they should all be afforded the widestpossible interpretation and vice versa.

The invention is not limited to the embodiments herein described whichmay be varied in construction and detail without departing from thescope of the invention.

1. A fixing for connecting an insulation layer to a precast concretepanel comprising: an insulation layer penetrating portion and a concretepenetrating portion contiguous with the insulation layer penetratingportion wherein the insulation layer penetrating portion comprises aflexible tie.
 2. A fixing as claimed in claim 1 wherein the insulationlayer penetrating portion further comprises a tension head attachable tothe flexible tie.
 3. A fixing as claimed in claim 2 wherein the flexibletie comprises a ratchet attachable to the tension head at a pawl.
 4. Afixing as claimed in claim 3 wherein the ratchet comprises through holesin the tie.
 5. A fixing as claimed in claim 3 or claim 4 wherein thepawl comprises a slot in the tension head.
 6. A fixing as claimed inclaim 5 wherein the tension head comprises a collar surrounding theslot.
 7. A fixing as claimed in any of claims 2 to 6 wherein the tensionhead comprises indents to define finger grips in the tension head.
 8. Afixing as claimed in any of claims 1 to 7 wherein the concretepenetrating portion comprises a wall plug.
 9. A fixing as claimed inclaim 8 wherein the wall plug comprises a substantially cylindricalhead.
 10. A fixing as claimed in claim 9 wherein the substantiallycylindrical head comprises at least one laterally extending fin formaximizing grip of the wall plug on concrete.
 11. A fixing as claimed inclaim 9 or claim 10 wherein the substantially cylindrical head comprisesat least one notch for maximizing grip of the wall plug on concrete. 12.A fixing as claimed in claim 8 wherein the wall plug comprises asubstantially T-shaped head.
 13. A fixing as claimed in any of claims 1to 12 wherein the concrete penetrating portion comprises a flange forstabilising the fixing in position during concrete pouring.
 14. A fixingas claimed in claim 13 wherein the flange extends laterally outwardsfrom the concrete penetrating portion.
 15. A fixing as claimed in any ofclaims 1 to 14 further comprising at least one rib for strengthening thefixing.
 16. A fixing as claimed in claim 15 wherein the at least one ribis provided on the insulation layer penetrating portion.
 17. A fixing asclaimed in claim 15 or 16 wherein the at least one rib is provided onthe concrete penetrating portion.
 18. A precast concrete panel systemcomprising a fixing as claimed in any of claims 1 to
 17. 19. A precastconcrete panel system as claimed in claim 18 wherein the systemcomprises a precast concrete panel reinforced with rebar and insulationfixed to the precast concrete panel by the fixing wherein the rebar andthe fixing are spatially separate within the system.
 20. A precastconcrete panel system as claimed in claim 18 or claim 19 wherein theinsulation layer comprises insulation board.
 21. A precast concretepanel system as claimed in claim 20 wherein the insulation boardcomprises expanded polystyrene.
 22. A method for forming an insulatedprecast concrete panel system comprising fixing an insulation layer to aconcrete panel with fixings as claimed in any of claims 1 to
 17. 23. Amethod as claimed in claim 22 comprising fitting the fixings to theinsulation layer via the insulation layer penetrating portion, layingthe insulation layer in a deck and pouring concrete into the deck toencapsulate the concrete penetrating portion of the fixings.
 24. Amethod as claimed in claim 23 further comprising the step ofconstructing a rebar in the deck before pouring the concrete.
 25. Amethod as claimed in claim 24 wherein the rebar is spatially separatedfrom the fixings to prevent thermal bridging.